RTOS，什么是硬实时和软实时

RTOS is real time operating system. It can response the outside event with a determinate time.
According to the response time, it can seperate into hard real time and soft real time opertation system.
In a hard real time os, then time of response is critical. If a processing event doesn't happen within a period time or not fast enough, the RTOS usually shut down the action and keep it from affecting the reliability or availability of the rest of the system. On the other hand a soft RTOS applications are more forgiving and let certain noncirtical miscues go by.